A pilot practicing aerial maneuvers was killed today after he nose-dived a vintage World War II plane into the waters off Long Island before more than 100 horrified spectators — including his own son, officials said.

Bob Baranaskas, 61 of Northport was killed when the single-engine plane splashed into the water at about 1:30 p.m. nearly 300 yards off Mastic Beach in the Suffolk County town of Shirley, police said.

Police said the pilot’s son, Chris, who is also a pilot, was on the beach when the crash occurred.

“There was not a day that my father didn’t climb into the cockpit and realize that he was entrusted with a piece of our American military heritage so that he could tell our country’s story,” the son said in a statement.

“He was in every sense of the world, my wingman and now my wingman is gone but our mission continues.”

Scores of people enjoying the beautiful weather watched as the plane went into a twirling nosedive from which it never recovered.

Helicopters and Coast Guard crews were still searching for the Baranaskas’ body.

“People were watching because of the tricks and then it just went right down,” said Roberta Fuentes, a witness from Bayside. “It was hard to believe your own eyes.”

Suffolk County cops said the pilot was practicing for an upcoming Memorial Day air show.

Officials described the plane as a privately-owned, authentic single seat P-40 War Hawk, the same type of plane that drew fire during the Dec. 7, 1941 Japanese attack on Pearl Harbor that pulled the US into World War II.

An oil slick marked the spot where the plane crashed. Helicopters and coast guard crews joined the search for the pilot’s body.

The plane crashed just east of the Flight 800 Memorial in Smith Point Park, which commemorates those killed when a Paris-bound TWA airliner carrying 230 passengers and crew exploded in 1996.

Baranaskas, a luxury home builder, flew the plane at parades and during holidays honoring veterans and soldiers.

“Bob was one of those handfuls of people who understood the enormous debt we owe our veterans and those still in uniform,” said US Rep Steve Israel (D-Long Island).